public class Rational{//有理数
    int numerator=1;//分子
    int denominator=1;//分母
    void setNumerator(int a){//设置分子
        int c=f(Math.abs(a),denominator);//计算最大公约数
        numerator=a/c;
        denominator=denominator/c;
        if (numerator<0&&denominator<0) {
            numerator=-numerator;
            denominator=-denominator;
        }
    }
    void setDenominator(int b){//设置分母
        int c=f(numerator,Math.abs(b));//计算最大公约数
        numerator=numerator/c;
        denominator=b/c;
        if (numerator<0&&denominator<0) {
            numerator=-numerator;
            denominator=-denominator;
        }
        else if (numerator>0&&denominator<0){
            numerator=-numerator;
            denominator=-denominator;
        }
    }
    int getNumerator(){
        return numerator;
    }
    int getDenominator(){
        return denominator;
    }
    int f(int a,int b){//求a,b的最大公约数
        if (a==0) {
            return 1;//c为分母不能为0
        }
        if (a<b) {//令a>b
            int c=a;
            a=b;
            b=c;
        }
        int r=a%b;
        while (r!=0) {
            a=b;
            b=r;
            r=a%b;
        }
        return b;
    }
    Rational add(Rational r){//加法运算
        int a=r.getNumerator();//返回有理数r的分子
        int b=r.getDenominator();//返回有理数r的分母
        int newNumerator=numerator*b+denominator*a;//计算出新分子
        int newDenominator=denominator*b;//计算出新分母
        Rational result=new Rational();
        result.setNumerator(newNumerator);
        result.setDenominator(newDenominator);
        return result;
    }
    Rational sub(Rational r){//减法运算
        int a=r.getNumerator();
        int b=r.getDenominator();
        int newNumerator=numerator*b-denominator*a;
        int newDenominator=denominator*b;
        Rational result=new Rational();
        result.setNumerator(newNumerator);
        result.setDenominator(newDenominator);
        return result;
    }
    Rational muti(Rational r){//乘法运算
        int a=r.getNumerator();
        int b=r.getDenominator();
        int newNumerator=numerator*a;
        int newDenominator=denominator*b;
        Rational result=new Rational();
        result.setNumerator(newNumerator);
        result.setDenominator(newDenominator);
        return result;
    }
    Rational div(Rational r){//除法运算
        int a=r.getNumerator();
        int b=r.getDenominator();
        Rational result=new Rational();
        if (a==0) {
            System.out.println("分母/除数不能为0");
            result.setNumerator(0);
            System.exit(0);
        }
        else{
            int newNumerator=numerator*b;
            int newDenominator=denominator*a;
            result.setNumerator(newNumerator);
            result.setDenominator(newDenominator);
        }
        return result;
    }
}